It is hypothesisized that a major subset of patients with absorptive hypercalciuria (AH) or idiopathic osteoporosis (IO) will demonstrate an upregulated state of the vitamin D receptor (increased fibroblast VDR number or VDR-complex activity). The aims of this study are 1) to carefully characterize both stone-formers and those with idiopathic osteoporosis who demonstrate an absorptive hypercalciuria pattern 2) to determine if these patients have an upregulated state of the 1,25-(OH)2D receptor in skin fibroblasts and 2) to determine by bone biopsy if the vitamin D receptor is upregulated in those subjects with low bone mass.